Producing printing surfaces



H. c. J. DEE KS PRODUCING PRINTING SURFACES Dec. 18 1923.

Original Filed March 6. L920 2 Sheets-Sheet l $5 awfozmm fam; 6

Dec. 18,1923. 1,477,866

I H. C. J. DEEKS rnonucme PRINTING suamcns Original Filed March 6'. 19202 Sheets-Sheet 2 Patented Dec. 31, B923.

H; C. 3'. DS, 01'' S CLIFF, NEW YORK.

PRODUCING PRINTING SURFACES.

Application filed March 6, 1920, Serial No. 363,855. Renewed May 9,1923.

To all whom it may concern:

Be it known that I, HIRAM C. J. DEEKS, a citizen of the United States,residing in Sea Cliff, county of Nassau, and State of 6 New York, haveinvented an Improvement in Producing Printing Surfaces, of which thefollowing is a specification.

My invention relates to the production of etchedjntaglio printingsurfaces for the ro- 10 tary printing process commonly calledrotogravure. More particularly, it relates to the formation of the acidresist and has for its. object the better control ofthe action exertedby the etching fluid upon the printing surface so that accurate tonevalues may be rendered in all parts of the picture.

It is well known that, although rotogravure printing has beenincreasingly used for several years and vast quantities of pictures arenow produced daily by this method. yet there is a distinct loss of themiddle tones and shadow detail in all such pictures.

They appear too hard and do not faithfully represent the tone value anddelicate detail of the photographic positive from which they were made.Notwithstanding this defect the appearance of these pictures more nearlyapproaches that of actual photographs than it is possible to obtain bythe "half-tone plate, offset, or other cheap printing method.

The object of my invention is to remedy the defect pointed out above andthus to make possible reproductions having all the charm of the originalphotograph without increasing the cost of producing the print-.

ing. roll or of altering the printing method in any way and putting,also, more control of the etching into the hands of the etcher. In moreparticular explanation of my invention, I will refer to the accompanyingdrawings, which are all, necessarily, much enlarged and of which Figure1 represents a sectional View, taken at right angles to the length ofthe roll, showing a portion of my improved resist upon the surface ofthe roll.

F i re 2 is a section, taken parallel to the length of the roll, showingthe same.

Figure 3 is a plan view of the same. Figure 4' shows the lines of thescreen pattern running diagonally insteadof parallel and at right anglesto the length of the roll.

Figure 5 is a section view of a ruled gratingtupon glass for forming thedoctor suppor Figure 6 is a plan view of same.

Figure 7 is a section View. of a grating upon a thin transparent supportsuch as celluloid.

Figure 8 is a plan view of same.

Figure 9 is a section view illustrating the action of light uponchromated gelatine when controlled by the interposition of a thingrating between the sensitive surface and a photographic plate.

The principle upon which the intaglio etching of a metal printingsurface, by the photogravure method, is based, depends upon theresistance of the etching fluid by a layer of gelatine which has beentemporarily (and for this specific purpose) applied to such metalsurface. layer is of different thicknesses obtained photographicallywhich thicknesses vary proportionately to the light and shadows of thephotographic positive image from which they were reproduced. Thegelatine retards the bitingaction of the etching fluid upon the metal,in proportion to its thickness at the point of action.

Where the term acid resist is used in this specification it is intendedto designate the hardened geiatine applied to the metal surface, whichhowever, as explained above, only retards the action of the etchingfluid. Thus the acid is usually perchloride of iron and the resist moreproperly a retarder.

Owing to the complicated chemical nature of gelatine and itssensitiveness to atmosoheric and other not easily controllableconditions and also to the wide variation of contrast which may readilyoccur between one photograph and another it becomes a matter of extremedifficulty to accomplish the etching with any degree of certainty.

It usually happens that those portions of the surface which are to printthe darkest become etched too deeply before the biting action hasstarted in those portions which are to print the lightest. This resultsin the hardness of the picture and the loSs of detail in the shadows,above referred to. To lessen this defect, resort is had to stopping theetching action in those portions, before it has proceeded too deep, bypainting over them with an acid resisting substance and then allowingthe action to continue in the The gelatine tic remaining portions. Thisis necessarily a V tlresome and expensive proceeding and does not effecta real correction of tone value.

As far as I am aware, the only other means which has hereto-fore beenpracticed for controlling the etching, has been by varying the strengthof the etching. fluid, it being well known that a concentrated solutionacts more gradually than a weaker one. This means however, is notsufficient to make any considerable correction possible and is,moreover,.both inconvenient and requiring of skill in manipulation.

In my improved method of forming the gelatine acid resist I'use theabove principle only partially and in conjunction with another which Ihave discovered and which, as far as I know, has not been applied tothis art before.

I refer to the fact that chromated gelatine, when exposed to lightbehind, and in contact with, a grating composed of transparent andopaque lines, becomes affected, in proportion to the amount of lightaction exerted upon it, not only as to depth but, also sideways. So thatif such a grating, made upon very thin transparent material, such ascelluloid, be interposed between a photographic plate and sensitizedcarbon tissue, in close contact therewith and exposed to light, it willbe found that, upon transfer-' ring the carbon tissue to a suitablesupport and washing away the unaltered gelatine together with the paperback in the'usual manner, the photograph will be reproduced, not only inlines of varying depth or thickness but of varying width also.

This effect can be enhanced, when making the exposure, by using twolights, separated from each other, and placed at certain angles inrelation to the sensitive surface and the direction of the lines of thegrating.

This arrangement is illustrated in Figure 9, which is a section viewtaken at right angles in the direction of the rating lines, wherein A isthe carbon tissue, is the grating upon their-support, C is thephotographic film showing varying degrees of density and C is the glasssupport thereof. The dotted lines D and D represent rays of lightproceeding from two separated sources, not Shown, but whose position isindicated by the angle of these dotted lines. The shaded portions A ofthe carbon tissue A represent the altered condition of the gelatine aseffected by the light rays D1 and D passing through the transparentportions of the grating B and further show how th1s alteration hasproceeded sideways as well as in depth in proportion to the amount oflight transmitted by the positive 0 In practicing my invention, I firstsensitize a piece of carbon tissue in the usual manner and expose it tolight through a parallel lined screen commonly called a grating.

This provides for very thin and uniform.

So far the proceeding is the same as ordinarily practicedexcept that Iuse a grating to accomplish this purpose whereas a crosslined screen isnow used. In both cases, the result is the same so far as preserving thesurface height against the doctor is concerned, provided that when agratingis used it is so arranged that the direction of the lines on theprinting roll [is contra-parallel,-

or nearly so, to the edge of the doctor blade.

Figure 5 represents a sectional view of a portion of such a gratingruled upon a thick glass support.- The number of rulings should be about150 to l inch. It will be seen that the opaque lines are much wider.

than the transparent spaces between them. This proportion shouldpreferably be about 5 to 1. The thickness of the glass support isunimportant but usually is about of an inch.

Figure 6 is a plan view of same. Thenext step, after having exposed thesensitized carbon tissue to light through the grating is to remove thegrating and expose the carbon tissue through the photographic positiveimage which it is desired to reproduce. Herein lies the principaldifference of procedure. In the ordinary course the positive is placedin contact with the tissue, which has been previouslyexposed through across-lined screen, and exposed to light for a su-flicient period.

In my method, I here interpose between the positive and the carbontissue, a grating on thin celluloid support, which I so arrange that thedirection of the lines of the same will be at right angles to that ofthe grating through which the carbon tissue has previously been exposed.Having brought the positive, thin grating and carbon tissue into closecontact by means of an ordinary printing frame, I now expose it to thecombined action of two separated light sources so arranged in relationto the sensitive surface and the direction of the grating lines, as toenhance'the sideways lightaction, from the edges of the grating lines,upon the gelatine, as illustrate-d in Figure 9.

Figure 7 is a sectional View of a portion of such a grating showing theopaque rulings upon the thin transparent support.

Figure 8'is a plan view of same.

tarmac The number of rulings should preferably be the same as thegrating used to form the doctor support, that is, about 150 to 1" inch.The proportion of the width of the opaque lines to the transparentspaces I prefer to have 1 to 1 or equal, but this may be varied, as mayalso the number of rulings, without interfering with the scope of thisinvention. The transparent support should be as thin as possible. Iprefer to use celluloid of .005 of an inch in thickness, for thisgrating.

Since this grating will transmit fiftyper cent of the light impingedupon it, I can, by using two lights, the combined intensity of which isdouble that ordinarily used, effect the exposure without substantiallyincreasing the time period.

After exposure, the subsequent steps of transferring the carbon tissueto the printing roll and washing away the paper back and unalteredgelatine, are the same as usual.

The novel form of acid resist, obtained in the manner explained above,represents the photograph in lines of hardened gelatine, Varying, notonly in depth but also in width, both correspondingly, to the light andshadows of the photograph, the direction of said lines being at rightangles to other, very narrow, lines of hardened gel-- atine, of uniform,width and thickness produced over the whole surface.

This formation is illustrated in Figures 1, 2 and 3. The shaded portionsA represent the hardened gelatin'e as affected by the light rays D and Dafter passing through the positive 0 and grating B, Figure 9. Theuniformly thin shaded lines A represent the hardened gelatine asaffected by exposure to light through the grating F, Figures 5 and 6. Erepresents a portion of the metal printing roll.

It will be seen that, instead of having, as in the usual method, anunbroken layer of gelatine (with thecrossed thin lines uniformly coverinthe metal surface) very thick in the hlgh lights, Very thin in theshadows and graduated accordingly for the various shades between, anddepending solely upon their different thicknesses and the variablenature of the gelatine, to retard "the biting action of the etchingfluid in the exact proportion desired, I have produced an acid resistcomprised of minute parallel lines of gelatine, varying both as tothickness and width in proportion to the various tone values of thepositive, and crossed at right angles by other, uniformly thin linesdesigned to preserve the surface height of the etching. The pictureforming lines may be completely joined together in the high light andalmost washed away in the deepest shadows, yet both these extremes andall,

the various shades between, will be represented by proportionate amountsof gelatine, broken up in the form of lines which proportionately varyin both depth and width, so that the etching fluid will have easy accessto the metal in all parts of the picture, but at the same time, will bemet with the requisite and proportionate amount of resistance toaccurately produce all the tone values represented.

In-the minute interstices of the-gelatine pattern, represented in Figure3 by the unshadedportions, it will be seen that the metal is bare to theetching fluid, and that the size of these minute b-ared places variesaccording to the lights and shadows of the picture. So that it will beunderstood that I produce my novel acid resist by forming a gelatinerelief and at the same timebreaking it up into lines havingproportionately varying covering power and use both the varying depthand varying width of these lines to better introduce the etching fluidto the metal and to more proportionately retard its action, thusproducing accurate tone values in all parts of the picture.

In most of the accompanying drawings, the lines of the pattern are shownas running parallel with or at right angles to the length of the roll.In practice,however, I prefer to have them run diagonally as illustratedin Figure 4.

Having now thoroughly explained my invention so that anyonefamiliar withthe art could practice it, What I claim as novel and desire to protectby Letters Patent is:

I claim: v

1. A metal printing roll for etching purposes comprising a photographicplate coated with an acid resist havlng pictureforming lines running inone direction, and surfaceheight-preserving lines runnlng in anotherdirection.

2. A metal printing roll for etching pur-- poses comprising aphotographic plate coated with an acid resist having parallelpicture-formin lines running in one direction, and parallelsurface-heIght-preserving lines runnin in another direction.

3. A metaI printing roll for etching purposes comprising a photographicplate coated with an acid resist composed of parallel picture-formilines running in one direction, and para lel surface-height-preservinglines running at right angles thereto.

4. A metal printing roll for etching purposes comprising a photographicplate coated with an acid resist composed of parallel gelatinepicture-forming lines running in one direction, and parallel gelatinesurfaceheight-preserving lines running at right angles thereto.

5. A metal printing roll for etching purposes comprising a photographicplate coated with an acid resist composed of parallel gelatinc lines ofproportionately varying depth and width running in one direction, andnarrow parallel gelatine lines of uniform depth and width running in theopposite direction.

6. A metal printing roll for etching purposes comprising a photo-graphicplate coated with an acid resist composed of parallel gelatine lines ofproportionately varying depth and width crossed by other narrow parallelgelatine lines of uniform depth and width.

7, A metal printing roll for etching purposes comprising a photographicplate coated with an acid resist composed of a gelatine relief broken upinto lines of proportionately varying width. 1

8. A metal printing roll for etching purposes comprising a photographicplate coated with an acid resist composed of gelatine lines ofproportionately varying depth and Width.

9. A metal printing .roll for etching purposes comprising a photographicplate coated with an acid resist formed by interposing a thin screenhaving minute opaque and transparent portions, between the photographicplate and the sensitive surface.

10. A metal printing rollfor etching purposes comprising a photographicplate coated with an acid resist produced by interposing a thin screenhaving minute opaque and transparent portions, between the photographicimage and the sensitized material, and in close contact therewith.

11. A metal printing roll for etching purposes comprising a photographicplate coated with an acid resist produced by interposing a thin screenhaving minute opaque poses comprising a photographic plate coated withan 'acid resist produced by .interposing a thin transparent material,having minute opaque rulings thereon, between the positive image and thecarbon tissue, during exposure to acute angled light rays.

13. A metal printing roll for etching purposes comprising a photographicplatecoated with a reticulated gelatine acid resist, composed of aseries -of narrow uniform lines running in one direction, crossing aseries of lines of varying depth and width running in an oppositedirection.

14. Ametal printing roll for etching purposes comprising a photographicplate coated with a reticulated gelatine acid resist, composed of aseries of narrow uniform lines, to form the surface-height-preservingwalls, running in one direction, crossing and intermingling with aseries of lines of proportionately varying depth and width, to form thetone values of the picture, running in the opposite direction.

In testimony whereof, I have signed my name to this specification this5th day of March, 1920.

' HIRAM C; J. DEEKS.

